Being on vacation I'll just chime in that upshift delay is non-existent on 500E's as they start in 2nd gear. Even reading Benzmac's literature I can find no reference to 500E upshift delay, it is a 400E/E420 thing. My car seems to get up to normal (80C and above) temp very quickly, quicker than the 400E ever did with upshift...
Michael is right about the differences in the lighting/wiring. You can get comparable results with some conversion work, the controls will just be different.
I'm pretty sure the wiper differences are in the arm somewhere. If a couple mm bug you that much, I suppose the conversion could be done.
If you are really serious about doing either conversion, let us know and we will be happy to help with P/N #'s via PartsShop.
hope this helps...Lee